19 questions, what to do, help, thank you

a-4│=│2a+7│

First Quadrant. a-4>0,2a+7>0

a-4=2a+7

a=-11p1(-15,-15)

Second quadrant. a-4<0,2a+7>0

4-a=2a+7

a=-1p2(-5,5)

Third Quadrant. a-4<0,2a+7<0

4-a=-2a-7

a=-11p3(-15,-15)

Fourth Quadrant. a-4>0,2a+7<0

a-4=-2a-7

a=-1p4 does not exist.

As for the non-existence of p4, it can be proved because it is in the fourth quadrant.

a-4>0,2a+7<0

Solution: a>4 and a<-3 2

There is no common solution for the two formulas, so there is no solution.

So there is no such point.

A-4 absolute value = 2a + 7 absolute value.

Four cases: a-4=2a+7

a+4=2a+7

a+4=-2a-7

a-4=-2a-7

Solve them separately and get four points.

Equal area method.

be×ac/2=ad×bc/2

be×8=6×12

be=9 triangle area: 6 12 2=36

be：36×2/8=9

Solution: The area of the triangle is certain.

·bc·ad=½·ac·be

be=ac·ad/bc

ac=8，ad=6，bc=12

BE=AC·AD BC=8·6 12=4The length of BE is 4

ad*bc/2=be*ac/2

As for the data, please substitute it yourself.

Original = cos37 degrees + 8 cos37 degrees + 2 cos37 degrees) (sin42 degrees cos11 degrees + cos42 degrees sin11 degrees).

11cos37 degrees sin (42 degrees + 11 degrees of early judgment) 11cos37 degrees sin53 degrees.

11 cos37 degrees to open cos37 degrees to annihilate the change.

Choose answer C

Connecting BE, CE proves that the triangle BEF is all equal to CEG, and both triangles have a right angle.

Because AE is an angular bisector, EF=EG

Because DE is a perpendicular bisector, EB=EC

So congruent.

Subtracting the formula to get x plus 2y is equal to 2 and solving a binary equation to get the value m.

The first cannot guarantee that the gas in the cylinder will be completely evacuated, and the second is because both oxygen and dioxoxide carbon can be solvented in water, and neither of the two types can guarantee the accuracy of the measured quasi-banquet sail.

co2+h2o=h2co3